The custom home in Durham, North Carolina features a standing seam metal roof, a balcony, a roof deck and a garden roof. The carport roof is made from solar panels. Photo: David Solow.

When Alison Trott purchased a vacant corner lot in the historic Cleveland-Holloway neighborhood in Durham, North Carolina, she wanted to use the space to construct her dream home. She wasn’t sure exactly what she wanted, but she had several priorities in mind. “When I built the house, I wanted to try and focus on sustainability as much as possible,” says Trott. “I wanted to try to focus on green building, and I wanted to try to utilize local resources as much as possible — local materials, local builders, local companies, and local craftsmen.”

She worked with a talented team of design and construction professionals to bring her vision to life, and the sustainable roof systems on the home became a crowning focus of the project.

At some point in the design process, the architect mentioned the possibility of incorporating a garden roof, and Trott jumped at the idea. “I said, ‘I want that!’” Trott recalls. “I was very excited about the idea, but I’d only seen green roofs on large commercial projects.”

The Lead Architect

Tina Govan, now principal of Somos Design, located in Raleigh, North Carolina, hit it off with Alison Trott right away. The two worked together on the design for several years, inviting CUBE design + research, an architecture firm in nearby Chapel Hill, to collaborate on the project.

The goals included constructing a modern home that would blend in with the historic neighborhood. The house was also designed to be part of the natural landscape. A key priority was saving two large oak trees on the property. “We wrapped the house around the trees,” notes Govan. “That way the house bends to nature.”

The key themes of the overall design are exemplified by the roof systems. The house features a metal gable roof with a balcony at one end, echoing historic homes in the area. The 950-square-foot garden roof was installed over the master wing of the house, and the roof of the carport was constructed from solar panels.

“It’s a very green house,” Govan notes. “Solar panels over the carport take care of most of the energy needs of the home. The green roof replaces what was disturbed — the ground below — and brings it up. The green roof blends well with the landscape, and with it the house doesn’t seem as big.”

The green roof is visible from many parts of the house, including the roof deck, which is separated from it by a glass railing. “I love green roofs,” says Govan. “They replace habitat and make building softer. It’s alive. It’s so much more dynamic and rich than any other type of hardscape.”

The Builder

Bob Wuopio is the owner of Form Design/Build LLC, headquartered in Raleigh, North Carolina. The company specializes in one-of-a-kind, complex projects, so this custom house was right up its alley. “We love unique projects,” Wuopio says. “Our preference is to make everything — the doorknobs, the pulls, the lights, the cabinets. We try to fabricate everything. That’s our niche.”

Located on a corner lot in the historic Cleveland-Holloway neighborhood, the modern home was designed to preserve two large trees and wrap around a courtyard to provide privacy. Photo: David Solow.

Numerous custom details throughout the house put the company to the test. For its relatively small footprint — 3,400 square feet — the house has its fair share of different roofing systems. “We have almost every type of roof system on that project,” says Wuopio. “We have a standing seam metal roof on the high gable. We have standing seam metal roof that becomes a metal wall. We have a built-up roof with a floating deck and a glass railing system. There is a green roof over a whole wing of the house.”

Getting the deck and green roof areas sloped perfectly was essential, and that begins with the substructure. “Getting a roof with a slope of 1/8 inch per foot right requires a pretty good framer,” Wuopio notes.

Form Design/Build served as the general contractor on the project, and Wuopio was responsible for scheduling multiple trades at the site. One key concern was making sure that the low-slope roof system wouldn’t be damaged after it was installed. “You don’t want anyone poking holes in it,” says Wuopio. “We spray foamed underneath the deck, so if you did have a small leak, you might not notice it for years, potentially.”

Wuopio knew the roof under the garden roof assembly was crucial. “I knew we needed a bulletproof roof, so I called Jim Pickard. He knew exactly what we needed.”

The Roofing Contractor

James Pickard III is the owner and president of Pickard Roofing Company Inc. in Durham, North Carolina. He represents the third generation of his family to run the business, which is more than 90 years old.

Pickard Roofing handles all types of commercial and residential projects, including historical restoration work. Most of the company’s projects are within 25 miles of the office, including this one, which was just two miles down the road.

The red metal roof is complemented with matching half-round gutters, which incorporate “rain chains” as downspouts. Photo: David Solow.

Crews at the company don’t do as much hot-mop BUR work as they used to, but they still have that club in their bag for below-grade waterproofing projects and garden roof assemblies. For this green roof project, Pickard recommended a coal tar pitch roof system. “We use hot-mopped coal tar pitch in situations where the material is in constant contact with water because the pitch doesn’t degrade,” Pickard notes. “You don’t want to have to take the dirt off of a garden roof and start looking for leaks. You have to do everything you can to make sure nothing can cause problems.”

That includes making sure the deck is secured with screws and not nails, which can back out and damage the roof assembly. Gravel stops should either be copper or stainless steel so they won’t corrode. “The whole idea is permanence,” Pickard says.

The hot-mopped system manufactured by Durapax consists of four plies of tar-coated fiberglass felt, which were set in four layers of coal tar pitch. A fifth layer of pitch was added as a top coat.

Pickard Roofing also installed the metal roof system. Snap Lock panels were custom fabricated in the company’s metal shop from 24-gauge Kynar-coated steel from Firestone Building Products in a wine-red color chosen by the homeowner. A synthetic underlayment, Titanium PSU 30 from InterWrap, was applied to the wooden deck before the panels were secured in place.

“The great thing about the Snap Lock system is there is virtually no fastening through the face of the metal,” Pickard says.

The 950-square-foot green roof covers one wing of the house. Pre-vegetated sedum mats were installed in most of the green roof area, and native plants are also featured in areas with more growing media. Photo: Living Roofs Inc.

“The panels are secured with cleats and clips in the seams.”

Snow guards from Berger Brothers were attached to the seams using non-penetrating screws. Half-round gutters were fabricated from the same metal as the roof and complemented with “rain chains” that serve as downspouts.

Many of the copper details and flashings were custom fabricated on site. “One of our strengths is in our flashing design,” notes Pickard. “The company has a lot of soldering irons. We still use a lot of the old techniques.”

The roofing installations went smoothly. As Pickard Roofing completed the roofs on the home, crews from Southern Energy Management, headquartered in Morrisville, North Carolina, constructed the carport roof from partially transparent solar panels.

“Everyone’s priority was on doing the job right,” Pickard says. “In this case, the emphasis was on the quality, not just the cost. The cost is important, don’t get me wrong, but in this case the budget was increased if there was a product that could do the job better. Ultimately, you have to put the quality where it counts, and that’s why this project worked out so well.”

The Green Roof Installers

Landscape architect Kathryn Blatt Ancaya co-founded Living Roofs Inc. in Asheville, North Carolina, along with her husband, Emilio Ancaya. The company handles all aspects of green roof and living wall projects, including design, installation and long-term maintenance. “Our work ranges from small residential projects to large complex commercial and institutional projects — and of course, everything in between,” she says.

These photos show the roof right after it was installed (left) and after three months of growth. Photos: Living Roofs Inc.

Living Roofs is a certified installer with garden roof system manufacturer Xero Flor America LLC, which is headquartered in Durham. Clayton Rugh, the director of Xero Flor, contacted the Ancayas after Trott and Govan toured the company’s own garden roof. They asked for help designing a version of the company’s lightweight extensive roof system for the project. As Rugh notes, “One of the benefits of the Xero Flor green roof system is its adaptability to nearly any roof situation — load limits down to 10 pounds per square foot, dynamic slope changes between zero and 45 degrees, and compatibility with most commercial waterproofing, including TPO, PVC, modified bitumen and asphaltic BUR assemblies.”

“We collaborated with the architect, Tina Govan, and Xero Flor to design an extensive pre-vegetated green roof with areas of deeper soil to support native grasses and perennials,” Ancaya explains.

The Living Roofs crew installed the Xero Flor XF300 green roof system with growing media depths ranging from 2.5 to 5 inches. After the root barrier was installed over the coal tar pitch roof, it was covered with a drain mat and filter fleece. The growing medium was then lifted into place using a telehandler.

Most of the garden roof area was overlaid with pre-vegetated Xero Flor sedum mats. Plugs of herbaceous plants were inserted in the deeper areas. “The grasses we used were grown by Hoffman Nursery, a local grower, and we used perennials by North Creek Nursery,” Ancaya notes.

The sedum mats are an attractive option because they are fully covered when they are installed, notes Ancaya. “Incorporating the areas of deeper soil also allowed us to create a more dramatic visual effect by contrasting the low-growing Xero Flor mats with taller and more textured plants,” she says.

The green roof installation took less than eight hours over the course of two days. “Kate is the design arm of Living Roofs, and Emilio is the installation arm, and the two of them teamed up on this project to knock it out of the park,” Rugh says.

A Happy Home

Trott enjoyed watching the building process. “I learned a ton,” she says. “I just love watching craftsmen who are passionate about what they do. I had fun out there!”

The home was completed in the spring of 2017, and Trott is thrilled with the result. “It’s better than I even imagined it would be,” she says. “I love it, and my cats love it. In fact, I think they are pretty sure that I did all of this just to entertain them.”

The growth and changing color palette of the rooftop garden has been interesting to watch. “The green roof has been amazing,” she says. “It’s just been one year, but the green roof keeps getting lusher and lusher. Every feature is my favorite feature in the house, but the green roof — I love it. I really do.”

In fact, Trott has become something of a residential green roof ambassador. “I’ve been spreading the word,” she says.

At the Ralph H. Johnson VA Medical Center in Charleston, a modular green roof system was installed to improve the quality of life for patients in the extended care wing.

Michael Whitfield was fascinated by the concept of green roofs, but he didn’t encounter many of them near his home in Charleston, S.C. He knew green roofs benefitted the environment, extended the life of roof systems and were aesthetically pleasing, so he was sure he could tap into the market in the Southeast as a green roof installer. When he couldn’t find a modular green roof system he liked, he designed his own. Whitfield is now the president and CEO of Green Roof Outfitters. Founded in 2009, the company manufactures components for green roofs installed all over the country. The company also installs green roofs itself, as was the case with a nearby hospital project.

After reading research studies that showed hospital patients recovered more quickly and needed less pain medication when they had a natural setting to look out on, Whitfield was inspired. He checked with local hospitals to see if there were areas that would be good candidates for green roofs. When the PR person at the Ralph H. Johnson VA Medical Center expressed an interest, Whitfield passed along the research material.

Months later he got a call asking him to submit a bid. While the hospital’s budget did not allow for a green roof to be installed on the entire building, there was a section of the roof that could be worked on right away. It was a 3,000-square-foot area on a wing for extended care patients, who looked out on a white TPO roof. “We put a green roof on that whole strip outside their windows so the patients would have something nice to look at,” Whitfield says.

Roof Materials

Construction took place on a weekend, when traffic would be lighter. A crane was used to load the material on the roof, including 4-inch-deep trays for the extensive modular green roof system and 2-inch-thick rubber pavers to go around the perimeter. Plants in the pre-grown mats included different varieties of sedum. Chives, prickly-pear cactus and other perennials were added later.

Green Roof Outfitters partners with growers around the country to provide pre-grown mats. Different varieties of plants are used in different parts of the country, but in most markets the company has had success with a blend using approximately 14 different varieties of sedum.

Whitfield believes the proper combination of plants is essential. “Two buildings that are right next to each other could have different microclimates, so you don’t know exactly what is going to work perfectly there and what is not,” he says. “We mix these plants with a variety—some do better in shade, some do better in sun. With the different tolerances they have, the strongest will survive, so we will always have something there. Many people make the mistake of planting one species they like with a certain pattern or color. But if you plant one species—a monoculture—and it doesn’t like it there, you’ll have a totally dead roof.”

Roof Report

The system does not require slip sheets for installation, but some roof manufacturers require them to maintain the warranty on the existing roof. In this project, a layer of 40-mil EPDM was placed on top the existing TPO roof. “We laid the modules on top of that,” says Whitfield. “We have rubber paver walk pads, which have feet on the bottom for drainage. We put those around the outside so we could have a nice-looking barrier and a walking area for the maintenance guys.”

Michael Whitfield was on hand to oversee the project at the VA medical center.

“Many people don’t know this, but a green roof can help the roof last 200 percent to 400 percent longer by preventing UV degradation,” Whitfield says. “It shades the roof and protects it. During the day, exposed roofs get superheated in the sun, and cool at night, so they are constantly expanding and contracting. A green roof system keeps it at a constant temperature.”

Another benefit can come from creating functional space on the roof. “We wholesale a lot of systems that combine a green roof with pavers to add usable space,” he says, “We can supply ipe wood pavers or other pavers in different configurations on our pedestal system to make walkways and patios.”

Depending on the environment, an irrigations system is a common option. “Green roof are a low-maintenance systems, not a no-maintenance systems,” notes Whitfield. “We incorporated irrigation channels into the new design of our modules, so you can put in irrigation during the installation or after it is completed.”

Another change is a smaller module. “Our modules used to be 2-feet-by-2-feet, but they were really heavy for the roofers,” he explains. “Our new modules are half the size—one-by-two—so they are much easier to handle and put in place.”

As they become more comfortable with green roof systems, roofing contractors are finding out they can be a valuable add-on with roofing projects. “Once roofers are on the site with all of the equipment and labor, why not make double the money by installing roofing and a green roof?”

No special training is needed to install this tray system. “It’s easy to install,” Whitfield notes. “The modules come fully vegetated, 40 to a pallet. You just pick one up, put it down, and repeat. It’s like laying down dominoes, honestly.”

The modular system is also easy to move if roof maintenance is necessary. “Our system is so flexible,” he says. “If you need roof maintenance, you can just pick up a couple of trays, move them and move them back. This is such an easy, modern way to do it—and it’s very affordable.”

The new Stanford Hospital is currently under construction in Palo Alto, Calif. The 824,000-square-foot facility connects to the existing hospital by a bridge and tunnel. The project includes a multi-level parking garage and with additional office buildings. Photo: Stanford Health Center.

Dennis Olson is used to dealing with large health care projects with multiple scopes of work, but the new Stanford Hospital project he’s currently working on might be the most challenging job he’s ever faced.

“I’ve never been involved with a project that’s been this complex and this difficult to roof and manage,” says Olson, the owner of Letner Roofing in Orange, Calif. “There are 16 different types of roofing and waterproofing systems, and each one is a little bit different at each location around the building.”

Located in Palo Alto, Calif., the new Stanford Hospital is an 824,000-square-foot facility that connects to the existing hospital by a bridge and tunnel. Olson is convinced his company is perfect for the job. He has been in the roofing industry for almost four decades, and he’s worked at Letner for more than 30 years. Olson worked his way up through the company as a foreman, project manager, and estimator before becoming the president and owner 15 years ago. “I have been estimating and managing health care projects for more than 25 years,” he says. “This job is right up our alley.”

The Company

Located in Orange, Calif., Letner Roofing specializes in commercial work including all types of roofing and below-grade waterproofing systems. “We are licensed with all of the major manufacturers to install their products,” Olson says. “We install basically every roofing and waterproofing system that’s available to the market. We have a sheet metal division that produces metal wall panels, roofing and general sheet metal.”

The new hospital features green roofs on the main hospital, central plant and parking structure. The garden roof section on level three of the main hospital building is shown here. Photo: Stanford Health Center.

Olson believes the company’s success begins with its great alliances with top general contractors and owners. “Our strengths are our customer service and quality control, and our ability to get projects done efficiently and on time,” he says. “I think that’s why general contractors choose us. We do what we say we’re going to do, we do it efficiently, and we take a lot of pride in the finished product.”

Communication is the key, according to Olson. “We have weekly sales meetings where all of the project managers and sales staff get together,” Olson says. “We share information, which allows us to learn from our failures and successes. It’s a team atmosphere. There is no real competition between the sales guys other than the innate competition that you each have to be better. We don’t compete against each other; we all work together for the common goal.”

Keeping the lines of communication open with industry partners is a key part of the puzzle. “As far as communication with the general contractor, that’s pretty simple, but a lot of people miss that,” he says. “You have to return phone calls. You have to return emails. If you have an issue on a project, handle the issue efficiently. Bring scheduling problems or details issues to the attention of the general contractor early. Nobody like to be surprised. People like to be informed.”

Due to their expertise in design-build situations, members of the Letner team are often called in by general contractors at the design and budgeting stage to offer advice on the right materials and methods for a project.

That was the case with the new Stanford Hospital project and general contractor Clark/McCarthy—a joint venture of Clark Construction Co. and McCarthy Building Cos. “McCarthy is a contractor I’ve been dealing with for more than 25 years. I’ve done a lot of health care projects with them, so when Stanford came out, they certainly wanted our input and help developing the budgets,” notes Olson.

Underground, Overhead

For Letner, the project involved several scopes of work including roofing on the main hospital and below-grade and underslab waterproofing.

Below-grade work included a pre-applied blind-side waterproofing application by Cetco. Letner also waterproofed underground tanks for domestic water, fire suppression, and sewage with a hot rubber system by Gaco Western. “The hospital was built for the worst-case scenario,” Olson notes. “If there is a big earthquake, and services are interrupted, the hospital can sustain itself for a while.”

This aerial photo shows the new Stanford Hospital, which is currently under construction. When completed in 2018, the complex will showcase 16 different roofing systems on 12 different elevations. Photo: Stanford Health Center.

As the superstructure was being completed, the roofing work began. “As I said, there are 16 different roofing systems on this project. There are 12 different elevations,” notes Olson.

Systems range from urethane and urethane and polymethyl methacrylate (PMMA) coatings to split-slab and inverted hot rubber systems, PVC roof systems and hybrid dual waterproofing system. The largest roofing systems include a Sarnafil PVC roof on the main hospital and a hot rubber system by Cetco for use under the garden roofs. Letner is installing garden roofs on the third floor of the main hospital and another on the central plant building.

Both of these garden roofs were constructed over flat concrete decks. The first step was to provide positive slope for drainage. Cell-Crete Corporation of Hayward, Calif., provided lightweight insulating concrete (LWIC), which was used to create positive slope. After the LWIC cured, crews from Cell-Crete installed quarter-inch cement board over the LWIC.

The hospital’s surgery rooms are directly beneath the garden roof on the main hospital, so the system has to be bulletproof. “This roof area requires intricate detailing along with a Cetco hybrid dual waterproofing system,” Olson states. “After the lightweight concrete and cover board are in place, Letner will install 60 mils of Hydrofix urethane membrane, followed by Cetco Corflex, a unique combination of a re-enforced KEE membrane bonded to an active polymer core membrane. Both garden roof areas will be protected with an in-place leak detection system by Internal Leak Detection.”

The overburden at the hospital garden roofs will include insulation, drainage mats, various types of plants and trees and pedestal paver systems.

Letner installed PVC roof systems from Sika Sarnafil level three of the hospital and on the main roof of the hospital. The 60-mil PVC membrane was installed over insulation and DensDeck cover board. Insulation was a minimum of R-20 near the drains. Some sections of the PVC were topped by ballast rock.

On the adjoining multi-level parking deck, Letner installed PVC roofs on two office buildings. The rest of the roofing and waterproofing work on the parking structure, including another garden roof, was completed by Courtney Waterproofing and Roofing of Irvine, Calif.

Safety Precautions

Letner and the general contractor help ensure safety is always top of mind at the site. “On this project, like any other, the safety issues were extremely important,” notes Olson. “We have our crews stretch and flex daily, and everyone must wear the personal protective equipment required for each task. Fall protection is a concern at every elevation, and hot rubber is extremely hazardous activity that requires additional protection and monitoring.”

Elastizell lightweight insulating concrete from Cell-Crete was used to provide slope for drainage on the flat structural concrete decks. It was later topped with cement board. Photo: Cell-Crete

The perimeter walls were being constructed during the project, so extra precautions had to be taken at the roof edge. “We had to wear harnesses and be tied off at all times,” Olson says. “We are very concerned about safety. We have a safety manager, and he does a very good job of identifying possible hazards on each job. We identify those per deck and apply the proper safety measures required for each elevation.”

Waterproofing the tanks also required special care. “The domestic water, waste and fire tanks and are in the ground, so you have to have people certified to do that work with specialized equipment,” Olson states.

Challenging Schedule

Construction of the hospital is still underway. Work is expected to be completed in 2018. The sheer size and multiple scopes of work were obvious challenges on the project, but the schedule was also tight—and subject to change. Some roof details were changed and others were developed as the job progressed, so Letner’s crews had to make some adjustments on the fly. Letner continues to work with the consultant on the project, ABB, to iron out the details.

“Sometimes you have to adjust the schedule when you are coordinating the work with other trades,” Olson notes. “The schedule, coordinating with other trades and the number of changes on the job have been the biggest issues we’ve faced. It’s is still a challenge, as the work is ongoing.”

When it came time to stage equipment and materials, the large job site suddenly seemed small. “The site was kind of tight, so of course logistics came into play with loading and off-loading each different area,” he says. “Some areas were hard to get to, and sometimes we had to wheel the product through corridors to get to the decks. Not everything was easy to get to. Logistics were difficult, but we were able to overcome those problems. Clark/McCarthy helped out quite a bit with logistics and loading.”

Despite the complexity of the job, the installation work has gone smoothly, according to Olson. “As far as the application for our field crews, there’s not that much difficulty for them. They are all very talented at what they do,” he says. “It’s just a very difficult building, and there are a lot of details that are not typical.”

The key to overcoming difficulties? “It’s constant communication,” Olson says. “Our strengths are our management teams, from the field operations to office staff. We’re honest with our customers. They understand the level of customer service and quality we deliver. Our success is a testament to the service we provide to our customers. We are often praised for our service and workmanship, and we are very proud of our quality installations as well.”

On the adjoining multi-level parking deck, Letner Roofing installed PVC roofs on two office buildings. The rest of the roofing and waterproofing work on the parking structure, including another garden roof, was completed by Courtney Waterproofing and Roofing. Photo: Stanford Health Center.

Maury Hall, U.S. Naval Academy, Annapolis, Md.

TEAM

The project included 34 dormers that feature double-lock standing-seam copper and fascia metal.

ROOF MATERIALS

Wagner Roofing was awarded the complete replacement of all roof systems. These included an upper double-lock standing-seam copper roof system, a bullnose copper cornice transition, slate mansard, 34 dormers with double-lock standing-seam copper and fascia metal, eight copper hip metal caps and a continuous built-in gutter with decorative copper fascia. Each of the dormers also had a copper window well.

The upper standing-seam roof was removed and replaced with 24-inch-wide, 20-ounce copper coil rollformed into 1-inch-high by 21-inch-wide continuous standing-seam panels that matched the original profile. The eave bullnose, which also served as the mansard flashing, was removed and returned to Wagner Roofing’s shop where it was replicated to match the exact size and profile.

The 34 dormer roofs were replaced with 20-inch-wide, 20-ounce copper coil formed into 1-inch-high by 17-inch- wide continuous standing-seam panels. The decorative ornate fascia of the dormers was carefully removed and Wagner’s skilled craftsmen used it as a template to develop the new two-piece copper cornice to which the roof panels locked. The cheeks and face of the dormers were also re-clad with custom-fabricated 20-ounce copper.

The oversized built-in-gutter at the base of the slate mansard was removed and replaced with a new 20-ounce copper liner custom-formed and soldered onsite. The replacement included a specialty “bull-nosed” drip edge at the base of the slate and an ornate, custom-formed fascia on the exterior of the built-in gutter. The decorative copper fascia included 85 “hubcaps”, 152 “half wheels” and 14 decorative pressed-copper miters. The original hubcap and half-wheel ornaments were broken down and patterns were replicated. Each ornamental piece was hand assembled from a pattern of 14 individual pieces of 20-ounce copper before being installed at their precise original location on the new fascia. The miters were made by six different molds, taken from the original worn pieces, to stamp the design into 20-ounce sheet copper.

In all, more than 43,000 pounds of 20-ounce copper was used on the project.

ROOF REPORT

Maury Hall was built in 1907 and was designed by Ernest Flagg. Flagg designed many of the buildings at the U.S. Naval Academy, including the Chapel, Bancroft Hall, Mahan Hall, the superintendent’s residence and Sampson Hall. His career was largely influenced by his studies at École des Beaux-Arts, Paris. Examples of Flagg’s Beaux-Arts influence can be found in the decorative copper adorning the built-in gutter on building designs.

Maury Hall currently houses the departments of Weapons and Systems Engineering and Electrical Engineering. The building sits in a courtyard connected to Mahan Hall and across from its design twin, Sampson Hall.

For most of the past century, the rooftops of commercial and institutional buildings have largely been places to locate unsightly mechanical systems. Architectural treatments, such as parapets and screens, provide visual relief from such equipment. Now, roofing professionals and building owners increasingly look at the roof as “found space”—a place to be planted and used, instead of hidden.

Throughout the U.S., garden roofs (or living roofs) are growing in popularity with more than 5.5 million square feet installed in 2014, according to Green Roofs for Healthy Cities. Most of that total was for private rather than public projects, indicating this is not just a government trend. In addition to providing attractive and usable open space, garden roofs offer environmental benefits, such as helping to slow and filter urban run-off.

Some of America’s largest companies have installed green roofs. Ford’s Dearborn, Mich., truck plant final assembly building sports one of the world’s largest living roofs at 454,000 square feet. In 2015, Facebook opened its MPK 20 office building in Menlo Park, Calif., with a 9-acre living roof featuring a 1/2-mile walking trail and more than 400 trees.

If you haven’t worked on a garden roof yet, it is likely only a matter of time until you do.

Addressing the Challenges of Garden Roofs

Adding plants and park-like amenities to a roof increases the complexity of the roofing assembly. Garden roofs present two primary challenges for roofing professionals to solve: minimizing the dead load and preventing moisture intrusion.

Weighing considerably less than soil, EPS geofoam is an ultra-lightweight engineered fill that can be used to create contoured landscape features, such as hills and valleys. The material weighs from 0.7 to 2.85 pounds per cubic foot, depending on the product type specified, compared to 110 to 120 pounds per cubic foot for soil.

Despite its low weight, EPS geofoam is designed for strength and has better load bearing capacity than most foundation soils. Geofoam’s compressive resistance ranges from approximately 2.2 psi to 18.6 psi (317 to 2,678 pounds per square foot) at a 1 percent deformation, depending on the product.

The garden roof on Facebook’s MPK 20 building provides ample open space and a 1/2-mile walking trail for employees.

EPS geofoam is also effective at addressing the second challenge of garden roofs: managing moisture absorption. The moisture performance of the various components in a green roof assembly is critical; retained water imposes additional loads on the roof and increases the risk of water damage to the roof assembly. EPS geofoam meeting ASTM D6817 standards works well here as it only absorbs 2 to 4 percent moisture by volume, even over long-term exposure, and it dries quickly. The moisture performance of EPS has been demonstrated in extensive in-situ applications and real-world testing, including research conducted by the U.S. Army Corps of Engineers’ Cold Regions Research and Engineering Laboratory. After burying EPS in wetted soil for nearly three years, the lab found that the material absorbed only 1.7 percent moisture by volume.

In addition to enabling lightweight, durable landscape features and helping to defend against water, EPS geofoam provides thermal insulation in garden roofs. Roofing professionals have used EPS insulation in roof assemblies for decades because it offers the highest R-value per dollar among rigid foam insulations.

Expect More Demand

Although green roofs currently account for a small portion of the billions of square feet of roofs in the U.S., expect to see more demand for them given their aesthetic and environmental benefits. High-performance materials, like EPS geofoam, can help provide a long-lasting, durable green roof assembly.

Commercial office properties have always had to contend for tenants as a part of doing business and, increasingly, existing buildings are facing stiffer competition from new office properties offering integrated amenities packages that go way beyond the lobby coffee shop. As a new generation of employees enters the workforce, employers are challenged to secure leases that provide more than simple office space, instead offering an attractive combination of recreation, retail and relaxation options that feel more akin to a resort than a workplace. In the case of Prudential Plaza, a 41-story structure in Chicago built in 1955, the challenge for the building owners was to offer new value in a building originally designed to respond to a workforce that no longer exists.

The rooftop transformation is highlighted by a fully wired amphitheater, fire-pit lounge and a small lawn accompanied by a new 12,000-square-foot fitness center and a 7,000-square-foot clubhouse located inside.

Investing more than $85 million into building renovations, Prudential Plaza’s owners envisioned a top-to-bottom rehabilitation, crowned by a 13,000-square-foot amenities deck on the 11th floor. The rooftop transformation is highlighted by a fully wired amphitheater, fire-pit lounge and a small lawn accompanied by a new 12,000-square-foot fitness center and a 7,000-square-foot clubhouse located inside. These amenities are exclusively for building tenants and their employees. Kyle Kamin, a Los Angeles-based CBRE Inc. executive vice president and tenant broker who has clients in Prudential Plaza called the roof deck “a game-changer with an unbeatable view.”

Engineering

Certainly the idea of a gorgeous tenant recreation and lounge area would appeal to most; however, few outside of the design and construction industry would appreciate the immense challenge of adding this type of space on top of a 60-year-old roof. When Wolff Landscape Architecture, Chicago, was asked to partner with Chicago-based architecture firm Solomon Cordwell Buenz for landscape design, project manager Ishmael Joya quickly understood the complexities of the situation. Joya is a landscape architect with 15 years’ experience, specializing in green-roof construction.

“Prudential Plaza is a classic figure in Chicago’s skyline and the first time we walked the project it was clear that the 4 1/2-inch-thick roof deck was going to present some design and construction challenges,” Joya remarks. Although the Wolff Landscape Architecture team has completed many green-roof projects, including renovations, Joya realized that adding what is essentially a mini-park to a very thin structural surface was going to require out-of-the-box thinking. “In any roof-deck renovation, it’s critical to reduce the weight of the building materials because the building is only designed to support a maximum amount of weight and that can’t be compromised,” he says.

Joya worked closely with the design team’s structural engineer, Wiss, Janney, Elstner Associates Inc., Chicago, to make sure the appropriate products were specified to support the expected weight of each area of the renovation

Demolition and Interim Roof

Like many large-scale occupied renovation projects, Prudential Plaza’s overall renovation was executed in multiple phases, allowing construction activities to take place while tenants maintained their typical routines. Romeoville, Ill.-based Preservation Services Inc., a commercial roofing company, was responsible for rehabilitating the original 11th-floor roofing structure. The original roof was a modified bitumen membrane that had been applied directly to a layer of lightweight concrete and covered by 2- by 2-foot pavers. Preservation Services carefully removed the pavers, old membrane and thin layer of concrete.

Investing more than $85 million into building renovations, Prudential Plaza’s owners envisioned a top-to-bottom rehabilitation, crowned by a 13,000-square-foot amenities deck on the 11th floor.

Because the building is located adjacent to a series of vaulted streets, the construction team was unable to use a high-reach crane because the weight of the crane would have required special provisions and necessitated street closures. Consequently, crews carried all removed debris down through the freight elevators during the night while the building was largely empty. At the end of each night, a single-ply EPDM membrane was rolled out, seamed and secured to protect the under structure from possible water penetration the next day.

Once demolition was complete, the EPDM was opened in select areas so repairs to the concrete slab could be made by other trades. When repairs were complete, a single layer of torch-applied modified bitumen membrane was applied to the deck along with additional structural steel required to support the added weight of trees, planters, patios and people. Finally, a white, granular-surfaced modified bitumen roof over tapered isocyanurate foam insulation was installed making the undersurface ready for the plaza deck renovation work.

Weight Considerations

Joya recommended a lightweight expanded polystyrene (EPS) material with high compressive strength that is used to reduce axial loading on structures. He has found the product very easy to work with, which saves time and money, ultimately allowing designers to put more of the client’s investment into tangible value users will see and feel rather than subsurface building materials.

On the Prudential Plaza roof-deck renovation, two types of EPS were used. EPS 15 was used in areas that would largely be filled with plants and wouldn’t bear much foot traffic. EPS 46, chosen for its high compressive strength, was used as a structural fill across the design’s many grade changes and in areas that would bear more weight of roof-deck occupants. For Joya, another advantage of using the EPS is being able to see the shape of the assembled product and make any required changes before the concrete is poured and work becomes significantly more complicated.

Team

Roof Materials

Because of the steep slope of this roof, the Columbia Roofing & Sheet Metal crew installed 60-mil Sureweld HS (High Slope) TPO. HS TPO contains more fire-retardant chemicals in the membrane to help decrease the spread of fire. In addition, 1/4-inch Securock Glass-Mat Roof Board was installed, which gave the building a Class A fire rating while helping protect against moisture and mold.

Roof Report

BMC Issaquah manufactures doors and high-end cabinetry. The industrial building features a 525-square barrel roof that was very wet and experienced dry rot. The crew replaced nearly 150 sheets of plywood throughout the project.

The main challenge during installation was safety because of the extreme slope. The barrel roof is nearly 60-feet tall from the bottom to the top of the barrel, making installation on the edges difficult because crewmembers had to hot-air weld rolled product on a nearly vertical surface. The HS TPO added another level of difficulty while welding along the edges.

How much traffic can a roof system bear? The fact is, live loads on roofs are getting much bigger as building developers and owners seek to allow more indoor-outdoor uses and rooftop amenities, such as seating areas, gardens and even fire pits and pools, which draw people to the roof. Plus, the dead load may be increasing thanks to those living material installations, such as planters and vegetative roof gardens. These assemblies usually require or hold water—adding to the dead load—as well as frequent maintenance and inspections, which mean a few more people (and more live load).

“We’ve known the benefits of a green roof from a water-management point of view for some time,” says Joshua Zinder, AIA, principal of JZA+D, Princeton, N.J., noting that more than 70 percent of the water that hits the roof is absorbed. “Increasingly, we see the roof as an opportunity for generating revenue or enhancing the value of the building. One of the ways we’re now helping developers reposition older office and industrial properties is by determining if we can create roof farms or indoor-outdoor spaces not only on the ground floor, but also on the roof planes.”

The case of the rooftop garden with public access is a growing trend, too, and “one must ensure that the roof structure has the necessary structural capacity to support rooftop activity,” notes Kelly Luckett, author of Green Roof Construction and Maintenance. Local codes vary for live loads and dead loads, he explains, and the project team calculates the green roof assembly as part of the total dead load. “Water in excess of that which saturates the growth media, snow and people visiting the green roof are all considered part of the live load of the structure,” Luckett adds.

Just as important, the roofing system has to resist the wear and tear of the live loading. The three main concerns for exposed structural elements, such as roofs, balconies and terraces, are protection from weathering, water ingress and environmental damage. Pedestrian walkways must also ensure long-term durability.

A look at the latest trends in “activating rooftops” reveals even more reasons for roofing contractors, architects and facility owners to look more carefully at specification documents and installation methods for these live-load roof zones.

A new Department of Sanitation complex in New York City, designed by Dattner Architects with WXY Architecture + Urban Design, both of New York, features a dynamic façade of moving metal fins and a 1.5-acre planted roof, which contribute to the LEED Gold operations. PHOTO: WADE ZIMMERMAN, COURTESY WXY ARCHITECTURE + URBAN DESIGN

Skylife and Community

For residential projects with rooftop terraces, careful specifying and installation of green roof assemblies is critical. “We like using liquid membrane roof and extensive green-roof systems, such as sedum carpet,” says Andrew Franz, AIA, LEED AP, principal of Andrew Franz Architect PLLC, New York, adding that the systems work well because the drainage mat is modular, lightweight, and easy to install and adjust—something that is important on uniquely shaped urban rooftop terraces.

Recent projects by Franz include a 2,800-square-foot garden terrace for a family of four in Manhattan. A bluestone floor extends from the dining area to the terrace’s softscape herb garden, further blurring the boundary between in-doors and out. “The green roofing system also includes a protection mat, which protects the roof membrane, a filter sheet of very lightweight soil to protect the drainage mat and the sedum carpet,” Franz says.

Other recent projects with active green roofs demonstrate the benefits of strong PVC membranes, such as at the modern 93 Bright Street townhouse in Jersey City, N.J., designed and developed by Jorge Mastropietro, AIA, whose firm JMA is based in New York City’s Soho neighborhood. Another example, called Trouthouse, designed and built by the Brooklyn-based thread collective, is a showcase of “passive design” principles that reduce energy use, recapture water and even allow for a roof-mounted shade structure that doubles as photovoltaic panels.

The new LEED Gold-certified facility for Gateway Community College in New Haven, Conn., was designed with a vegetative roof to create a new community area on the top floor. According to construction manager Providence, R.I.-based Dimeo Construction, which worked with Providence-based Gilbane Building Co. and the New York office of architect Perkins+Will on the project, the “multi-level student gathering area steps up from the ground floor to a rooftop garden. The green roof also supports photovoltaic panels on a special framing system.”

A panel of IDC members, who are all registered interior designers, judge product entries based on design objectives, design and technical innovation, market application, and sustainability. Entries are scored on a 0-100 scale, with Gold-level awards requiring a score of at least 90. Only five of the 30 product winners, including Porous Pave, attained the Gold standard. Among this year’s winners, Porous Pave was the only outdoor product for landscaping, hardscaping and on-site stormwater management applications.

The IIDEXCanada award is Porous Pave’s second honor this year. BUILDINGS magazine selected Porous Pave as a 2015 Money-Saving Product. Porous Pave was one of the superior building products showcased for commercial building developers, owners and facility managers in the magazine’s June 2015 issue.

Since performing its first concert in 1939, the West Michigan Symphony, a professional orchestra in Muskegon, Mich., has been a vital part of the region’s cultural landscape. In spring 2013, the symphony decided it was time to expand its administrative and ticketing services. It moved into offices in the newly renovated Russell Block Building. Located in downtown Muskegon, a block away from the Frauenthal Theater where the orchestra performs its concerts, the historic Russell Block Building was constructed in 1890.

The porous-paving material had to express the musical note motif the landscape architect envisioned for the patio. It is the quintessential design element for the entire rooftop project.

“With the move, the symphony also realized a long-held dream: establishing a flexible space where we could expand educational offerings and stage smaller fine-arts performances,” explains Carla Hill, the symphony’s president and CEO.

Named The Block, the 1,800-square-foot space offers seating on two levels for up to 150. In addition to providing an intimate venue for a variety of arts performances, The Block is available for meetings and special events. The west-facing windows of The Block look out toward Muskegon Lake. However, there was a problem: Outside the windows, an unimproved and unappealing tar roof marred the view.

“In conversations with the symphony and Port City Construction & Development Services, which planned and managed the building renovation, we started envisioning the transformation of the unadorned roof into a rooftop patio and garden,” says Harry Wierenga, landscape architect, Fleis & VandenBrink Inc., Grand Rapids, Mich.

Wierenga designed a 900-square-foot green roof (including 380 square feet of vegetation and a 520-square-foot patio area) as an accessible and appealing outdoor space. His design invites patrons of The Block to the outdoors onto a landscaped rooftop patio.

First Things First

“The existing roof was a tar roof over a concrete deck. Some holes had been boarded over and patched with tar,” notes Gary Post, manager, Port City Construction & Development Services LLC, Muskegon. “If the rooftop patio and garden had not been incorporated into the project, we would not have replaced it. We had to reroof to support the new rooftop outdoor space.”

The Port City Construction & Development Services roofing crew removed the existing roof down to the concrete deck, which they repaired. Two new roof drains were added to improve drainage. A single-ply membrane was selected for the new roof. The crew fully adhered the new membrane to the deck. The crewmembers then installed a geotextile fabric to protect the membrane and rolled out a geotextile drain sheet atop the protection fabric. The drain sheet facilitates drainage to the existing and two added roof drains.

A new 40-inch-high wall around the perimeter shelters the space and enhances rooftop safety. The porous paving’s gray and black custom-color mix harmonizes with the color of the wall.

A new 40-inch-high wall around the perimeter was constructed to shelter the space and enhance rooftop safety. Preparations also included widening the opening out to the rooftop from the interior of The Block. Glass double doors would be installed to establish a generous and transparent transition from indoors to outdoors.

Permeable Pavement

The project team applied a multi-faceted set of factors in evaluating options and selecting a pavement material for the patio:

To eliminate standing water and allow excess stormwater to flow to the drains, the paving material had to be permeable.

The plan called for installing the patio and green-roof elements on top of the geotextile drain sheet. The paving material would have to work with the modular green roof selected for the project.

The paving material had to be lightweight. By regulation, the maximum static plus live load for the roof is 100 pounds per square foot.

For easy access and safety, the pavement had to be low profile to minimize the threshold at the entry into The Block.

To create visual interest within the rectangular shape of the roof, the design emphasizes irregular shapes with angles to break up the space. The paving material would have to be flexible to adapt to the design.

The musical-note motif Wierenga envisioned for the patio is the quintessential design element for the entire rooftop project. The paving material had to offer the versatility to express the design.

Finally, a green-building product was preferred.

The project team considered composite decking and pavers. However, these linear materials were not flexible enough to adapt to the shape of the patio or sufficiently versatile to convey the musical note design.

Sponsored Messages

@roofingmag on Twitter

November/December 2018

Read our latest issue in digital format.

About Roofing

Roofing is a national publication that unravels, investigates and analyzes how to properly design, install and maintain a roof system. Through the voices of professionals in the field, Roofing’s editorial provides a unique perspective.